The Chaperone Protein Cct5 is Essential for Hematopoietic Stem Cell Maintenance.

Proper proteostasis is indispensable for the long-term maintenance of hematopoietic stem and progenitor cells (HSPCs). The TRiC/CCT (chaperonin-containing TCP-1) complex, a key constituent of cellular machinery facilitating accurate protein folding, has remained enigmatic in its specific function within HSPCs. Here we show that conditional knockout (KO) of Cct5 significantly impairs the maintenance of murine HSPCs. Primary and secondary transplantation experiments unequivocally demonstrate the incapacity of Cct5 KO HSPCs to reconstitute both myeloid and lymphoid lineage cells in recipient mice, highlighting the pivotal role of the TRiC/CCT complex in governing these cellular lineages. Furthermore, leveraging an integrated approach that merges a Protein-Protein Interaction (PPI) database with RNA sequencing (RNA-seq) data of HSPCs, our analysis reveals intricate interactions between Cct5 and vital transcription factors crucial for HSC homeostasis. Notably, Cct5 engages with MYC, PIAS1, TP53, ESR1, HOXA1, and JUN, intricately regulating the transcriptional landscape governing autophagy, myeloid differentiation, and cytoskeleton organization within HSPCs. Our study unveils the profound significance of TRiC/CCT complex-mediated proteostasis in orchestrating the maintenance and functionality of HSPCs.

Aspartyl-tRNA synthetase 2 orchestrates iron-sulfur metabolism in hematopoietic stem cells via fine-tuning alternative RNA splicing.

Aspartyl-tRNA synthetase 2 (Dars2) is involved in the regulation of mitochondrial protein synthesis and tissue-specific mitochondrial unfolded protein response (UPRmt). The role of Dars2 in the self-renewal and differentiation of hematopoietic stem cells (HSCs) is unknown. Here, we show that knockout (KO) of Dars2 significantly impairs the maintenance of hematopoietic stem and progenitor cells (HSPCs) without involving its tRNA synthetase activity. Dars2 KO results in significantly reduced expression of Srsf2/3/6 and impairs multiple events of mRNA alternative splicing (AS). Dars2 directly localizes to Srsf3-labeled spliceosomes in HSPCs and regulates the stability of Srsf3. Dars2-deficient HSPCs exhibit aberrant AS of mTOR and Slc22a17. Dars2 KO greatly suppresses the levels of labile ferrous iron and iron-sulfur cluster-containing proteins, which dampens mitochondrial metabolic activity and DNA damage repair pathways in HSPCs. Our study reveals that Dars2 plays a crucial role in the iron-sulfur metabolism and maintenance of HSPCs by modulating RNA splicing.